Stabilized extreme pressure lubricant



Patented Oct. 5, 1943 STABILIZED EXTREME PRESSURE LUBRICANT Bertrand W. Story, Wenonah, and Francis M.

Seger, Pitman, N. L,

um Oil Company, Incorporated, New N. Y a corporation of New York assignors to Socony-Vacu- York,

No Drawing. Application December 23, 1941, Serial No. 424,128

9 Claims. (01. 252-35) This invention has to do with the art of extreme pressure lubrication and contemplates the development of extreme pressure lubricants of improved stability under abnormally high More speoperating temperature conditions. ciflcally, 'this invention is concerned with the improvement of. extreme pressure lubricants of the type described in U. S. Patents Nos. 2,153,- 495 and 2,153,496. Extreme pressure agents described therein are reaction products obtained by replacing part of the chlorine in a polychlorinated aliphatic material or a polychlorinated material of predominately aliphatic nature, with a thiocarbonate group. Extreme pressure lubricant bases of the type shown in the aforesaidpatents may be broadly designated as chloraliphatic thiocarbonates, a specifically preferred product of which is designated chlornaphtha xanthate and is obtained by reaction of a chlorinated petroleum naphtha with an alkali alkyl xanthate. Lubricants containing these extremepressure agents are'for normal extreme pressure uses highly effective and quite satisfactory. It has been found, however, that under abnormally high operating temperature conditions-in excess of 225 F.there is a pronounced 'tendency for the lubricant to form undesirable deposits of black sludge.

The present invention is predicated on the surprising discovery that extreme pressure lubricants of the aforesaid typema-y be stabilized against the formation of undesirable deposits of sludge by incorporating therein minor proportions of heavy metal soaps, such as lead naphthenate. Typical heavy metal soaps contemplated herein are those wherein the heavy metal is lead; coppenzinc, iron, chromium, manganese, etc., and the organic-soaplike radical may be naphthenate, sulphonate, oleate, stearate, etc.

We are aware 'of the fact that lead naphthenate and other heavy metal soaps have been used alone in extreme pressure lubricants; It has also been proposed in the prior art to use lead naphthenate in combination with extreme pres sure bases of the active sulphur type to inhibit corrosion, etc. For example, lead naphthenate is added to extreme pressure lubricants of the latter type to reduce corrosion induced by the active sulphur type of extreme pressure agent, especially that corrosion which would be produced in the presence of water. However, lubricants containing the chlornaphtha-xanthate type of extreme pressure base, the improvement of which is contemplated herein, are especially non-corrosive, whether dry or wet; and

in lead naphthenate adds nothing to their stability in this regard.

Combination of the particular E. P. base of the chloraliphatic thiocarbonate type and lead metal soap such as lead naphthenate distin-,

guishes-over the lead soap-active sulphur extreme pressure lubricants of the prior art, in the manner in which the "two particular" types of additives cooperate at abnormally high operating temperatures to give improved results. The customary physical and chemical tests of our lubricant containing lead naphthenate are not appreciably altered from those of a lubricant in which the metal soap is absent, but there is a pronounced change in service characteristics. The lubricant which does not contain lead naphthenate will deposit a film of black material ranging from a sticky varnish to a granular sediment on the parts of a test gear set when the operating temperature is maintained at about 300 F. The same lubricant containing our sulphurchlorine material and lead naphthenate, when used under the same conditions, will leave the gears bright and clean. The magnitude of this improvement is dependent upon the amount of heavy metal soap present in the lubricant containing the chloraliphatic thiocarbonate or chlornaphtha xanthate extreme pressure base and upon the operating conditions, length of time, temperature maintained, etc. In all cases, however where abnormally high temperatures are encountered the metal soap substantially retards the sludging tendencies oi the lubricant containing the aforesaid sulphur-chlorine, extreme pressure agent without affecting, positively or negatively, the corrosiveness of the lubricant.

Although the nature of this action is not fully understood, we believe that the improvement is eflected by the combination of two actions:

(1) hydrochloric acid isformed by the cracking of the sulphurand chlorine-containing extreme pressure lubricant at abnormally high-opcrating temperatures, andthis acid is removed by reaction with the heavy metal soap,

(2) the metal chloride formed in the aforesaid reaction has a gentle polishing action which aids in keeping the gear parts free from deposits.

' naphthenate and a chlornaphtha xanthate reaction product was compared with lubricant compositions containing onlythechlornaphtha xanthate, by means of the four-square stability test in a machine designed specifically for this work. The machine and test are described by the following:

The tests were conducted in two Boston type TA gear reducer units equipped with steel spiral gears of and 32 teeth respectively, in each unit. The low speed shafts of these units were coupled together while the high speed shafts were connected to each of two spur gears of equal size, meshing with each other and mounted in a third gear box unit. With this arrangement a ,gear train square.was formed.

The gear train was driven by a 2 horsepower motor connected to an extended shaft from one of the spur gears, providing a speed of 1800 R. P. M. for the high speed and 536 R. P. M. for the low speed shafts of the test units.

In order to develop a test oil temperature of 300 F., a tooth load was applied to the spiral gears by means of a static thrust with one end of the high speed shaft in one of the test units. With the rigid coupling of the units in the square, this load or tooth pressure was transmitted in approximately the same amount to all gears in the train including the second testunit. The thrust loading device consisted essentially of a lever system with weights, and a thrust bearing mounted at the end of the unit shaft. Its most important feature was the fact that the load could be appliedor adjusted for the desired temperature while the machine was in operation.

After thorough cleaning with solvents and wire brushing, the units were set up in the machine for a run. After the test oils had been charged to each of the two test units, the machine was started with no load. The beginning of the test was recorded when the first weights were hung on the loading lever. Additional load was applied gradually to bring the oil temperatures up to 300 F. in from 1 to 1% hours after starting the test. The testing period included this time for warming up.

In order to furnish semi-automatic temperature control of the oil, thermostatically-operated heat lamps were directed on the sides of the test units, one lamp on each unit.

The chlornaptha xanthate reaction products used as extreme pressure bases in the tests were obtained by following the general procedure described in U. S. Patents 2,153,495 and 2,153,496 referred to above. Preparation of a typical reaction product consists essentially of first chlorinating a petroleum naphtha, a predominantly aliphatic material containing from about five to about carbon atoms, until it contains about 50% to 55% by weight of chlorine. Two hundred parts of this product were dissolved in about 500 parts of a relatively low boiling solvent, as, for example, acetone, and placed in a reaction vessel heated by a water jacket and equipped with stirrer and reflux condenser. parts of potassium xanthate were added, and the mixture held at the boiling temperature, with stirring, under reflux, for about two hours. The resulting mixture was cooled to room temperature, filtered, and the filtrate subjected to distillation to remove the acetone. After removal of acetone, the product was washed to remove potassium salts, dried, and filtered. The finished reaction product was a dark brown liquid, containing about 12% of sulphur and about 37% of chlorine. About 250 parts of product were recovered. Variation in sulphur and chlorine content can be obtained by varying the degree of chlorination of the naphtha and by varying the amount of potassium xanthate used, to give a group of xanthochlornaphthas of wide varying compositions. The nature of the light aliphatic hydrocarbon my also be varied, as well as the solvent,'which may be ethyl or methyl alcohol, methyl ethyl ketone, or the like.

A mineral oil base, of Saybolt Universal Viscosity of 95 secs. at 210 F., having incorporated therein 10% of a chlornaphtha-xanthate reaction product (chlorine content about 23% and sulphur content about 11%) was subjected to the foregoing test for 25 hours. At the end of the test, the unit had a light coating of black lacquer over most of the interior and parts, and a considerable amount of soft sludge was found in the bottom of the oil base. The same mineral oil composition with 5% of lead naphthenate subjected to the same test for 25 hours illustrated the surprising superiority of our combination, for the rollers of the bearings were very bright, and no other residue than a. gray powder was deposited on the parts.

Similarly comparative tests of 25 hours were run on one mineral oil composition comprised of a hypoid lubricant of Saybolt UniversalViscosity of 90 sees. and 10% of a chlornaphtha-xanthate reaction product (chlorine content about 32% and sulphur content about 11%); and on Then about 120 the same mineral oil composition having added thereto about 3% of leadnaphthenate. The oil composition without lead naphthenate gave a moderate soft sludge deposit on the gear and bearings, and a slight to moderate deposit of granular material in the oil base. On the other hand, the oil composition with lead naphthenate gave only a black lacquer deposit on the gear and bearings, no soft sludge deposits and no granular material in the oil base.

The relative amounts of chlorine and sulphur, or, more specifically, of chlorine and thiocarbonate characterizing groups, in the extreme pressure bases in combination with heavy metal soaps as contemplated by the present invention, may be varied over a relatively wide range. In general, it may be said that the reaction product should preferably be one which contains from about 25% to 40% chlorine and from about 7% to 15% sulphur. Expressing the sulphur content as the equivalent amount of characterizing thiocarbonate groups present in the product, these preferred products are more accurately identified as containing fromv about 10% to about 22% characterizing dithiocarbonate or xanthate (divalent OCSz) groups or from about 7% to about 17% characterizing trithiocarbonate (divalent CS3) groups. For general purposes it may be said that the characterizing thiocarbonate-' group-content is about 22%.

And, as aforesaid, the heavy metal soaps contemplated by this invention are those formed from the heavy metals-lead, copper, zinc, iron, chromium, manganese, etc., and such organicsoaplike radicals as naphthenate, sulphonate, oleate, stearate, etc.

In compounding the lubricant compositions contemplated herein, mineral lubricating oil is preferred as the carrying medium. It is our intention, however, to include within the scope of this invention other carrying media, such as animal oils, vegetable oils, and light mineral oil distillates, in which these extreme pressure agents and heavy metal soaps may be dispersed With substantial permanence either as true solupreferably from about 7% to tions or as colloidal suspensions. The. concentration of the ingredients used in the suspending or carrying medium may be varied, depending upon the conditions of use, the carrying medium, etc. In general, theconcentration of the sulphurand chlorine-containing materials contemplated herein may be said to range from 1% to 20%; and the heavy metal soaps to substantially retard the deposition of sludge, etc., under operating temperatures in excess of 225 F., in general may range from about 0.5% to about We claim:

1. A lubricant product for use where high unit pressures are combined with high rubbing speeds and high operating temperatures, consisting of a mineral lubricating oil having in admixture therewith: a minor proportion, suflicient to impart extreme pressure characteristics to said lubricant product, of a substantially non-corrosive product obtained by chemically substituting a part only of the chlorine in a chlorinated aliphatic material containing from about five to about fifteen carbon atoms with a thiocarbonate group; and a minor proportion, sufficient to sub-. stantially retard sludging at operating temperatures in excess of 225 F., of a heavy metal soap.

2. A lubricant product for use where high unit pressures are combined with high rubbing speeds and high operating temperatures, consisting of a mineral lubricating oil having in admixture therewith: a minor proportion, sufficient to impart extreme pressure characteristics to said lubricant product, of a substantially non-corrosive product obtained by substituting a part only of the chlorine in a chlorinated aliphatic material containing from about five to about fifteen carbon atoms with a xanthate group; and a minor proportion, sufficient to substantially retard sludging at operating temperatures in excess of 225 F., of heavy metal soap.

3. A lubricant product for use where high unit pressures are combined with high rubbing speeds and high operating temperatures, consisting of a mineral lubricating oil having in admixture therewith: a minor proportion, sufficient to impart extreme pressure characteristics to said lubricant product, of a substantially non-corrosive product obtained by substituting a part only. of the chlorine in a chlorinated aliphatic material containing from about five to about fifteen carbon atoms with a xanthate group; and a minor proportion, sufiicient to substantially retard sludging at operating temperatures in excess of 225 F., of a lead soap.

carbon atoms with a xanthate group; and a minor proportion, suflicient to substantially retard sludging at operating temperatures in excess of 225 F., of lead naphthenate.

5. A lubricant product for use where high unit pressures are combined with high rubbing speeds and high operating temperatures, consisting of a mineral lubricating oil having in admixture therewith: a minor proportion sufllcient to impart extreme pressure characteristics to said lubricant product, of a substantially non-corrosive chlorinated aliphatic hydrocarbon having from about 5 to about 15 carbon atoms in which a part only of the chlorine has been chemically substituted with a xanthate group, said product having a chlorine content of from about 25% to about and a characterizing xanthate group content of from about 10% to about 22%; and a minor proportion, sufficient to substantially retard sludging at operating temperatures in excess of 225 F., of lead naphthenate.

6. A lubricant product for use where high unit pressures are combined with high rubbing speeds and high operating temperatures, consisting of a mineral lubricating oil having in admixture therewith: a minor proportion suificient to impart extreme pressure characteristics to said lubricant product, of a substantially non-corrosive chlorinated petroleum naphtha in which a part only of the chlorine has been chemically substituted with an alkyl xanthate group, said product having a chlorine content of from about 25% to about 40% and a characterizing xanthate group content of from about 10% to about 22%; and a minor proportion, sufiicient to substantially retard sludging at operating temperatures in excess of 225 F., of lead naphthenate.

'7. A lubricant product for use where high unit pressures are combined with high rubbing speeds and high operating temperatures, consisting of a mineral lubricating oil having in admixture therewith: from about 1% to about 20% of a chlorinated petroleum naphtha in which part of the chlorine has been chemically substituted with an alkyl xanthate group, said product having a chlorine content of from about 25% to about 40% and a characterizing xanthate group content of from about 10% to about 22%; and a minor proportion of from about 0.5% to about 10% of lead naphthenate.

8. A lubricant product for use where high unit pressures are combined with high rubbing speeds and high operating temperatures, consisting of a mineral lubricating oil having in admixture therewith: a minor proportion, sufiicient to impart extreme pressure characteristics to said lubricant product,-of a. chlorinated petroleum naphtha in which apart only of the chlorine has been chemically substituted with an alkyl xanthate group, said product having a chlorine content of from about 25% to about 40% and a characterizing xanthate group content of from about 10% to about 22%; and a minor proportion of lead naphthenate sufficient in amount to substantially retard sludging at operating temperatures in excess of 225 F.

9. A lubricant product for use where high unit pressures are combined with high rubbing speeds and highoperating temperatures, consisting of a mineral lubricating oil having in admixture therewith: a minor proportion, sufilcient to impart extreme pressure characteristics to said lu-- bricant product, of a substantially non-corrosive product obtained by chemically substituting a part only of the chlorine in a chlorinated aliphatic material containing from about five to about fifteen carbon atoms with a thio-carbonate group; and a minor proportion of a heavy metal soap sufilcient in amount to substantially retard sludging at operating temperatures in excess of 225 F.

BER'I'RAND W. STORY. FRANCIS M. SEGER. 

